Tungsten (W) film deposition using chemical vapor deposition (CVD) techniques is an integral part of semiconductor fabrication processes. For example, tungsten films may be used as low resistivity electrical connections in the form of horizontal interconnects, vias between adjacent metal layers, and contacts between a first metal layer and the devices on a silicon substrate. In an example tungsten deposition process, a barrier layer is deposited on a dielectric substrate, followed by deposition of a thin nucleation layer of tungsten film. Thereafter, the remainder of the tungsten film is deposited on the nucleation layer as a bulk layer. Conventionally, the tungsten bulk layer is formed by the reduction of tungsten hexafluoride (WF6) with hydrogen (H2) in a chemical vapor deposition process.
Tungsten films may also be used in various memory applications, including in formation of buried wordline (bWL) architectures for dynamic random access memory (DRAM). In an example of bWL deposition, a tungsten layer may be deposited on a titanium nitride (TiN) layer to form a TiN/W bilayer by a CVD process using WF6.